Chapter 7: The Skeletal System
Learning Objective #1: Identify and describe the five functions of the skeletal system.
1) Support: the skeleton provides a structural framework for the attachment of organs. (Example: muscles)
2) Protection: the skeleton protects internal organs from damage. (Example: the rib cage protects the lungs and heart)
3) Aid in Movement: bones are rigid and serve as levers against which muscles pull to provide movement.
4) Blood cell formation: blood cells are manufactured in the red marrow of bones.
5) Storage: bones act as a storage site for two minerals calcium and phosphate. These minerals in ion form are needed for biological activities. (Example: muscle contraction)
Mar 8­9:13 AM
Chapter 7: The Skeletal System
Learning Objective #2: Distinguish between long bones, short bones, flat bones, and irregular bones and provide an example of each.
Long bones: greater in length than in width. (Femur)
Short bones: equal in length and width. (Bones of the wrist)
Flat bones: thin and flat. (Cranium)
Irregular: complex shapes that do not fit into any other category. (Vertebrae)
Mar 8­9:26 AM
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Chapter 7: The Skeletal System
Learning Objective #3: Identify the parts of a typical long bone.
Diaphysis: the long central shaft of a long bone.
Epiphyses: the ends of the bone that form joints with other bones.
Articular cartilage: a thin layer of hyaline cartilage that covers the ends of the epiphyses.
Periosteum: a dense sheet of connective tissue that covers the bone and is responsible for bone growth and repair.
Mar 8­9:42 AM
Compact bone: tightly packed bone that forms the walls of the bone.
Spongy bone: a lattice structure of bone spicules that are cemented together and provide a home for red bone marrow.
Red marrow: blood forming tissue.
Medullary Canal: large central chamber in the center of long bones.
Yellow Marrow: rich fatty tissue in the center of bones used for energy storage.
Endosteum: thin membrane that lines the inside of the Medullary canal.
Mar 8­9:52 AM
2
Chapter 7: The Skeletal System
Learning Objective #4: Describe the inorganic and organic components of bone tissue, and distinguish between the three types of bone cells on the basis of their function.
Inorganic components of bone:
Mineral Salts:
1) Calcium phosphate
2) Calcium carbonate
**These two minerals combine to form hydroxyapatite**
3) Minerals salts make up 2/3 of the total weight of bone.
4) These salts form a very dense matrix that restricts even the passage of blood vessels.
Mar 8­2:45 PM
Chapter 7: The Skeletal System
Organic components of bone:
Collagen is the primary organic component of bone and serves as a matrix to further strengthen and reinforce the matrix.
Three types of bone cells:
1) Osteoblast: cells responsible for deposition of collagen and mineral salts. Osteoblasts build bone.
2) Osteocytes: bone cells that are trapped by the matrix, they maintain bone in their immediate area.
3) Osteoclasts: bones cells that wander through bone tissue secreting substances that dissolve mineral salts.
Osteoclast clean­up bone. Useful in bone remodeling and repair of bone fractures.
Mar 8­2:52 PM
3
Chapter 7: The Skeletal System
Learning Objective #5: Describe the microscopic structure of compact bone, and compare it with that of spongy bone.
Lamellae
Osteon or Haversian System
Volkmann's canal
Osteonic or Haversian canal
Mar 9­8:53 AM
Chapter 7: The Skeletal System
Learning Objective #5: Describe the microscopic structure of compact bone, and compare it with that of spongy bone.
Mar 9­9:09 AM
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Chapter 7: The Skeletal System
Learning Objective #5: Describe the microscopic structure of compact bone, and compare it with that of spongy bone.
Compare and contrast spongy and compact bone:
Spongy bone
Compact bone
1) Porous
1) Dense
2) Thin sheets of bone (trabeculae)
2) Tightly packed concentric rings of bone. (Osteons)
3) Avascular matrix with blood 3) Highly vascular
vessels that travel through canals and canaliculi.
Mar 9­9:18 AM
Chapter 7: The Skeletal System
Learning Objective #6: Explain the process by which intramembranous bones are formed.
1) Precursor cells (stem cells) transform into osteoblasts.
2) Osteoblasts cluster near embryonic membranes.
3) Osteoblast begin forming spongy bone through the cementing of thin bone plates.
4) Osteoblast eventually become trapped in the bone matrix (lacunae) and become osteocytes.
5) Osteoblast near the embryonic membrane (periosteum) start forming compact bone.
Mar 9­9:24 AM
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Chapter 7: The Skeletal System
Learning Objective #7: Describe how endochondral bones are formed from cartilage. Snow
a) An endochondral bone begins as a model of hyaline cartilage in an embryo.
b) It soon forms a collar of early bone around its midsection.
c) The primary ossification center forms as cartilage is replaced by spongy bone. Once formed, it proceeds to expand as more blood vessels penetrate the area.
d) A central cavity is formed, and secondary ossification centers begin to emerge.
e) Ossification continues until spongy bone fills the epiphyses and compact bone surrounds the entire structure. Hyaline cartilage remains in the epiphyseal plates and the articular cartilages (the epiphyseal plates provide for lengthwise bone growth until young adulthood).
Mar 9­9:37 AM
Chapter 7: The Skeletal System
Learning Objective #8: Describe the process of bone growth in length and width.
Interstitial growth: this is a lengthening growth where the cartilage in the epiphyseal plate is replaced by bone and the cartilage continues to grow outward. Lengthening growth continues until the chondroblast cease functioning.
Appositional growth: this is a widening growth as osteoblast in the periosteum continue to deposit bone material. Additionally, osteoclast reabsorb mineral salts from the medullary cavity, widening the medullary canal. This deposition and removal is unequal, thus resulting in a bone not only widening, but thickening over time.
Mar 9­2:27 PM
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Chapter 7: The Skeletal System
Learning Objective #9: Define the role of one remodeling in maintaining homeostasis.
1) Depositing excess minerals like calcium and phosphate in the bones for storage.
2) In times of low mineral supply, bones can release minerals necessary for maintaining homeostasis.
3) This is an important aspect of repairing and healing damaged bone.
Mar 9­2:40 PM
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